DE2728606A1 - PROCESS FOR OBTAINING EPSILON CAPROLACTAM FROM AN EPSILON CAPROLACTAM SULFUR ACID REACTION MIXTURE - Google Patents

Description

Dr. F. Zumstein Sr. - Dr. Ξ. Assnarn - Dr. R. Koenigsberger Dipl.-Phys. R. Holzbauer - Dipl .-! I.y. F. Kln ^ seiser - Dr. F. Zumstein jun.

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BRAUHAUSSTRASSE 4 STAMICARBON B.V., GELEEN (Netherlands) Process for obtaining e-caprolactam from an e-caprolactam Sulfuric acid reaction mixture onsgemis

The invention relates to a method for obtaining e-caprolactam from an ε-caprolactam-sulfuric acid reaction mixture, As is the case, for example, with the Beckmann rearrangement of cyclohexanone oxime with the help of sulfuric acid, oleum or. Sulfur trioxide, or at the Production of caprolactam by reaction of cyclohexanecarboxylic acid with a nitrosating agent in the presence of sulfuric acid.

The lactam can thereby be extracted from the lactam-sulfuric acid reaction mixture in a known manner (see e.g. American patent specification 2,993,889) obtained by neutralizing the sulfuric acid in the reaction mixture with ammonia water to form ammonium sulfate and then separates the lactam from the ammonium sulphate produced.

A disadvantage of this process is that a large amount of ammonium sulfate is obtained as a by-product, for which a suitable one is not always available

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Sales market is available. According to the American patent specification 3,336,298, nan can avoid this disadvantage if one uses the im The reaction mixture to be processed does not contain sulfuric acid neutralized with ammonia water to form ammonium sulfate, but the sulfuric acid by adding ammonium sulfate to ammonium hydrogen sulfate reacted and the lactam separated by extraction from the ammonium hydrogen sulfate. A concentrated aqueous ammonium hydrogen sulfate solution then remains which can be used, for example, to digest rock phosphate. In the case of such a work-up, there is nothing Ammonium sulfate as a by-product, but the extraction of the lactam is linked to the manufacture of another product. One A method for obtaining the lactam without the formation of by-products is described in US Pat. No. 3,852,272. At this Method, the sulfuric acid is partially neutralized with ammonia water and remains after the extraction of the lactam from the partially neutralized Mixture back an aqueous solution containing ammonium hydrogen sulfate, which is burned to form sulfur dioxide, whereupon the sulfur dioxide is added to form the lactam-sulfuric acid reaction mixture required sulfuric acid can be implemented. The disadvantage of this process is the ammonia losses during the combustion of the ammonium hydrogen sulfate, because the ammonia in the ameonium hydrogen sulfate is completely too Nitrogen and water is burned.

A method is disclosed in American patent 3,879,380 described in which no by-products are produced and no ammonia is burned. In this process, the sulfuric acid becomes partially neutralized to form an ammonium hydrogen sulfate melt, after which the ammonia and the sulfur trioxide are obtained separately from this melt with the aid of a suitable metal oxide such as zinc oxide. However, this production of ammonia and sulfur trioxide is extremely expensive.

The object of the present invention is now a process for the production of caprolactam from the aforementioned reaction mixture, in which no by-products need to be generated and the combustion of ammonia can largely be avoided.

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The process according to the invention for the production of g-caprolactam from an e-caprolactam-sulfuric acid reaction mixture, in which the Sulfuric acid is partially bound in the form of ammonium salt and that Lactam is separated from the partially bound sulfuric acid by means of extraction, is characterized in that part of the partially bound sulfuric acid undergoes thermal decomposition with the formation of a Gas mixture containing ammonia and sulfur dioxide is subjected to this gas mixture with the remaining part of the partially bound sulfuric acid is brought into contact with simultaneous binding of the ammonia to the sulfuric acid and removal of the sulfur dioxide in gaseous form and that the ammonium hydrogen sulfate and / or ammonium sulfate obtained in this way for partial binding of the caprolactam-sulfuric acid reaction mixture ch is used sulfuric acid.

The sulfur dioxide removed in the process according to the invention can be converted into sulfuric acid or oleum in a known manner; this sulfuric acid or the oleum can be used to prepare the starting reaction mixture.

Those present in the partially bound sulfuric acid Ammonium salts of sulfuric acid can be found in several known ways Ammonia and sulfur dioxide are decomposed. You can use the ammonium salt with a reducing agent such as sulfur or carbon monoxide at a Let the temperature of ISO - 400 ° C react (see the Dutch Patent application 7,297,028). You can also do this at a temperature of 370 - 390 ° C coal (see Dutch patent application 282,684) or

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at a temperature of 400 - 600 C use the combustion products of an oil or gas burner (see Btitische patent specification 1.014.945) as a reducing agent.

The warmth of the thermal decomposition Gas mixtures can be used very well for preheating and / or concentration use the bound sulfuric acid, which is subjected to thermal decomposition. The touch of the ammonia and sulfur dioxide Gas mixture with the remaining part of the partially bound sulfuric acid can take place, for example, by introducing this gas mixture into a column through which the liquid phase is in countercurrent with the gas mixture

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while at the same time removing the resulting neutralization heat is pumped. For this contact, others known per se can also be used Methods are used.

If no raw material losses occur in the process according to the invention, and the composition of the partially bound sulfuric acid des Ammoniuawasserstoffsulfate corresponds to, is a distribution of partially bound sulfuric acid in two equal parts and the caprolactam is obtained without the need for sulfuric acid and ammonia will. In practice there will always be losses, e.g. of ammonia during thermal decomposition, which must be supplemented; the applicable Distribution of the partially bound sulfuric acid can therefore deviate from the theoretically optimal distribution.

The invention is explained with reference to the figure and the example, without being restricted to these.

In the figure, A represents a reactor for converting cyclohexanone oxime into f-caprolactam, B represents a neutralizer for partial neutralization of the lactam-sulfuric acid mixture, C a Extraction system for extracting the lactam from the partial Neutralization of the lactam-sulfuric acid-qamish, oynes Neutralizer for complete or partial neutralization of the ammonium hydrogen sulfate, E a device for reducing decomposition of the ammonium hydrogen sulfate and F a sulfuric acid / oleum plant. Via a line 1, cyclohexanone is fed into the Italagerungsreaktor A, e.g. a mixing reactor or a vessel equipped with a stirrer with a mixing cyclone, which is also fed via a line 2 with sulfuric acid or oleum, produced in the sulfuric acid / oleum plant F, is fed. The mixture flows through a line 3 to the neutralizer B, into which a solution of ammonium sulfate and ammonium hydrogen sulfate from the ammonium hydrogen sulfate neutralizer D, Introduced via a line 5 ammonia and via a line 14 water will. Of course, the ammonia and the water can be completely or partially replaced by ammonia water. That to ammonium hydrogen sulfate neutralized rearrangement mixture flows via a line 6 to the extraction system C, into which a solvent is introduced via a line 7 for caprolactam is initiated in which sulfuric acid, ammonium sulfate and ammonium hydrogen sulfate are poorly soluble, e.g. benzene, toluene, 1,2-dichloroethane, chloroform, 1,1,2,2-tetrachloroethane, ethyl ether

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or dibutyl carbinol. Id extractant is dissolved caprolactam Discharged via a line 13 from the system and into a not shown Apparatus for the extraction of the lactam. The resulting aqueous Ammonium hydrogen sulfate solution is discharged via a line 8. Part of the ammonium hydrogen sulfate solution discharged via line 8 is introduced into the decomposition device E via a line 10 and, under reducing conditions, is converted into an essentially ammonia, Gas mixture containing sulfur dioxide and water vapor decomposes. This gas mixture is introduced into the neutralizer D via a line 11, the remaining part of the aqueous ammonium hydrogen sulfate solution via a line 9, which originates from the extraction device C and is supplied via line 8, is introduced. In the neutralizer D, ammonium hydrogen sulfate is converted into ammonium sulfate with the aid of the ammonia in the gas mixture emerging from line 11. A gas mixture essentially containing sulfur dioxide escapes from the neutralizer D and is transferred to the sulfuric acid / Oleum plant F initiated. By evaporation of the line 10 in the Decomposition plant With the solution discharged, the water content can be kept at the desired level. The neutralizer D becomes the accumulating ammonium sulfate / ammonium hydrogen sulfate solution - if necessary after Cleaning - transported to neutralizer B via line 4.

Embodiment

According to the scheme shown in the figure, about 100 tons of e-caprolactam are produced per day. The neutralization of the Lactam-sulfuric acid-gamish takes place under atmospheric pressure

at a temperature of 40 C. The resulting e-caprolactam is extracted with chloroform. The ammonium hydrogen sulfate obtained during the neutralization is in the manner described in British patent 1.014.945 with the help of natural gas according to the gross equation NH ₄ HSO ₄ + CH ₄ + Ii O ₂ ->. Thermally decomposed NH ₃ + 3 H ₃ O + CO _2.

The composition of the individual material flows in kmol / h is in shown in the table below.

In this exemplary embodiment, the nitrogen

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in the form of ammonia to 70% and the sulfur in the form of sulfur dioxide 100% recovered from the ammonium sulfate / ammonium hydrogen sulfate solution.

Head Oxime Oleum * NH_ NH.HSO./ CHC1_ SO _n Lactam

1 37.6

2 56

3 56 37

4 56

5 17

6 112 37

7 230

8 112

9 56

10 56

11 39 56

12 56

13 230 37

calculated as H.SO.
2 4

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Claims (1)

- 7 - 2827 PATENT CLAIMS \\ λ process for recovering ε-caprolactam from a c-caprolactam, sulfuric acid reaction mixture in which the sulfuric acid is partially bonded in the form of ammonium salt and the lactam is separated by extraction from the partially bonded sulfuric acid, characterized in that part the partially bound sulfuric acid is subjected to thermal decomposition with the formation of a gas mixture containing ammonia and sulfur dioxide, this gas mixture is brought into contact with the remaining part of the partially bound sulfuric acid with simultaneous binding of the ammonia to the sulfuric acid and removal of the sulfur dioxide in gaseous form and that the Ammonium hydrogen sulfate and / or ammonium sulfate obtained in this way is used to partially bind the sulfuric acid present in the caprolactam-sulfuric acid reaction mixture. 2 «C-caprolactam obtained using the method according to a of the preceding claims. 709852/1197 ORIGINAL INSPECTEO